KR20000070781A - Creping adhesive and process for creping tissue paper - Google Patents

Abstract

The present invention relates to an adhesive applied to a creping surface in the process of dry creping the tissue paper. The adhesive includes cationic starch, and any polyvinyl alcohol and water soluble thermoplastic cationic polyamide-epihalohydrin resin. This adhesive provides good adhesion and removal in dry creping.

Description

Creping adhesive and process for creping tissue paper

Sanitary paper tissue products are widely used. Such products are commercially available in a format suitable for various conditions, such as cosmetic tissues, toilet tissues, and absorbent towels. The forms of the products, i.e. basis weight, thickness, strength, sheet size, dispensing medium, etc. are often very different, but they are tied in a common way since they are of the same origin in that they are produced by a process called a crepe papermaking process .

Creping is a method of mechanically compressing paper in the machine direction. As a result, not only many physical properties change significantly, especially in the machine direction, but the basis weight (mass per unit area) increases. Creping is generally performed using a flexible blade called a doctor blade for a Yankee dryer during machine operation. This blade is sometimes called a creping blade or simply a scraper.

Yankee dryers are generally large drums of 8 to 20 feet, which are designed to pressurize with steam to provide a hot surface in order to complete the drying of the papermaking web at the end of the papermaking process. On small spherical forming carriers, such as fourdrinier wires (which do not require large amounts of water to disperse the fiber slurry), the first formed paper web is usually a felt or fabric called a press. to the fabric, where the paper is mechanically compressed or continuously dehydrated by any other dehydration method, such as through-drying with hot air, and finally the Yankee dryer in a semi-dry state. Move to the surface of to complete the drying.

The impact of the bonded web and the doctor blade is essential to give the paper web the properties that manufacturers seek. Particularly important physical properties are ductility, strength and bulk.

Softness is the tactile sensation that a consumer perceives when a product is held, rubbed on the skin, or wrinkled by hand. This feel is determined by a combination of several physical properties. One of the most important physical properties associated with ductility is generally considered by the person skilled in the art to be the stiffness of the paper web used to manufacture the product. In other words, stiffness is generally considered to depend directly on the strength of the web.

Strength refers to the ability of the product and its constituent webs to retain physical integrity and not to tear, torn and torn during use.

The term bulk, as used herein, refers to the inverse of the density of a tissue paper web. This is another important part of the true and perceived performance of the tissue paper web. Bulk improvement generally imparts water absorbency to fabrics. Part of the bulk of the tissue paper web is given by creping.

The degree of adhesion of the papermaking web to the dryer is also very important because it relates to the crepe blades on which the rolls of paper are formed and the control of the movement of the web in the space of the winding period. Insufficiently bonded webs do not control the sheet well, which makes it difficult to form a uniform paper reel. Loose sheets between the scraper and the reel will result in entanglement, fold or curl of sheet ends in the wound paper. Poorly formed rolls affect the reliability of papermaking operations as well as subsequent tissue and towel making operations that convert the rolls into tissue and towel products.

The degree to which the paper web is adhered to the dryer is also very important because it relates to the drying of the web. Higher adhesion reduces heat transfer disturbances and allows the web to dry faster, allowing for more energy efficient and faster work.

However, the degree of adhesion is not the only variable in determining product quality and manufacturing reliability. For example, some adhesives have been found that form a bond between the web and the doctor blade at the creping point so that the web does not move properly so that some of the web remains adhered to the dryer and passes without the blade ends. This causes the web to fail and often breaks the web.

It is also essential that a small amount of adhesive accumulate on the dryer, but some types of adhesive may result in excessive accumulation or streaks. Streaks can cause differences in the adhesive profile across the width of the dryer. This may cause a bump or entanglement in the final paper roll. A second doctor blade is often placed after the crepe blade to remove excess creping adhesive and other residue. This blade is called a cleaning blade. The cleaning blades and crepe blades are changed in some cases to prevent loss of streak coating and sheet adjustment.

As used herein, the term "doctorability" refers to the ability to relatively easily remove the web from the dryer without the occurrence of defects or the need for frequent blade replacement to prevent excessive accumulation.

One important property of creping adhesives is that they are rewetable. As used herein, the term "rewettability" means that when the web is in contact with the heated dry surface, the adhesive film that remains on the heated dry surface by the moisture contained in the semi-dry tissue web is activated. It means ability. A significant increase in stickiness is an indicator of high rewetability. Rewetability is important because at any rotation of the Yankee dryer only a portion of the dry surface is normally covered with an adhesive. Adherence of the sheet to the dryer occurs mainly by means of crepe adhesive means previously passed through and deposited.

It is a natural trend for papermaking webs to adhere to a cylindrical dryer due to the accumulation of deposition of water soluble components in the paper web. These water soluble components form an adhesive film that is rewet at the point where the web moves to the cylindrical drum. However, the need for certain levels and types of adhesives has led to significant activity among researchers in the art. Accordingly, various crepe adhesives are known in the art. For example, the use of animal glue has long been known.

Bates also discloses a method for improving the adhesion of a web comprising applying aqueous polyvinyl alcohol in US Pat. No. 3,926,716, which is incorporated herein by reference.

As Bates pointed out, the need for specific adhesion of the web to the dryer drum is particularly desired when the papermaking process is of the pattern dense category. Dense patterned webs are characterized by relatively high density areas dispersed within the high bulk area, including more recent advances where relatively high density areas are continuous and high bulk areas are discontinuous. One method of making a patterned dense tissue paper web is called air drying. The web of dense pattern is particularly problematic for the adhesion of the paper web to the rotary drying cylinder. This is because the web is fixed to the dryer cylinder in the high density region. This creates a problem with adhesion because the web must be delivered to the rotating cylinder at relatively high fiber concentration levels not only due to the less surface area contacted with the dryer, but also due to the lower efficiency of the cylindrical dryer resulting from less contact surfaces. Relatively small amounts of water can cause the adhesive film to rewet at the point where the web moves to the dryer, making it more difficult for webs dried at relatively high fiber concentrations to adhere to the dryer.

As another example, Soerens describes an adhesive comprising an aqueous mixture of polyvinyl alcohol and a water soluble thermosetting cationic polyamide-epihalohydrin resin in US Pat. No. 4,501,640.

While many adhesives have been disclosed and commercially available, including these examples, a single adhesive or adhesive blend did not provide satisfactory doctorability, rewetability and adhesion.

It is therefore an object of the present invention to provide an adhesive for creping tissue paper and a method of applying the adhesive which overcomes the above limitations by providing improved adhesion while maintaining removability.

These and other objects are achieved through the present invention, which will be described later.

Summary of the Invention

The present invention is an aqueous dispersion useful as a creping adhesive comprising cationic starch.

Cationic starch has from about 0.001 to about 0.2 cationic substituents per anhydroglucose unit of starch. Preferably, the cationic substituent is selected from the group consisting of tertiary aminoalkyl ethers, quaternary ammonium alkyl ethers and mixtures thereof.

The dispersion contains about 90 to about 99.9% water, more preferably about 95% to about 99.9% water.

Preferably the starch accounts for about 10% to about 70% of the dry weight of the dispersion, and the dispersion further comprises polyvinyl alcohol. The polyvinyl alcohol is preferably partially hydrolyzed polyvinyl acetate having a degree of hydrolysis of at least about 80%, more preferably from about 80% to about 95%.

The molecular weight range of the polyvinyl alcohol useful in the present invention is from about 90,000 to about 140,000. An indirect measure of molecular weight is viscosity, as used herein refers to that of a 4% aqueous dispersion of polyvinylalcohol at 20 ° C. The polyvinyl alcohol of the present invention has a viscosity of at least about 20 centipoise, most preferably at least about 35 centipoise.

A further embodiment of the invention is an aqueous dispersion comprising cationic starch and further comprising a water soluble thermosetting cationic polyamide-epihalohydrin resin.

The polyamide-epihalohydrin resin preferably comprises the reaction product of polyamide and epihalohydrin containing secondary or tertiary amine groups. Epihalohydrin is preferably epichlorohydrin and the polyamide amine group is preferably a secondary amine group derived from polyalkylene polyamides and saturated aliphatic dibasic carboxylic acids.

The molar ratio of epihalohydrin and secondary amine groups in the polyamide is from about 0.5: 1 to about 2: 1.

Another preferred embodiment of the invention is an aqueous dispersion comprising from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein the solids are from about 10% to about 70% cationic starch. , About 20% to about 85% polyvinyl alcohol, and about 5% to about 40% water soluble thermosetting cationic polyamide-epihalohydrin resin.

The present invention also provides a method for creping tissue paper. The method of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein the solids contain cationic starches having from about 0.001 to about 0.2 cationic substituents per anhydroglucose unit of starch. Applying an aqueous dispersion comprising a rotary creping cylinder;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

c) contacting the web with a doctor blade to remove it from the creping cylinder.

Another preferred embodiment of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein from about 50% to about 90% of the solids comprises from about 0.001 to about 0.2 cations per anhydroglucose unit of starch Applying an aqueous dispersion to the rotating crepe treatment cylinder, wherein the aqueous dispersion is cationic starch with a sexual substituent and from about 10% to about 50% of the solid is a water soluble thermosetting cationic polyamide-epihalohydrin resin;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

and c) contacting said web with a doctor blade to remove it from the creping cylinder.

Another preferred embodiment of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein from about 10% to about 70% of the solids is from about 0.001 to about 0.2 cations per anhydroglucose unit of starch Cationic starch with a cyclic substituent, about 5% to about 40% of the solids are water soluble thermosetting cationic polyamide-epihalohydrin resins, and about 20% to about 85% of the solids are about polyvinyl alcohols. Applying the aqueous dispersion to the rotary creping cylinder;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

and c) contacting said web with a doctor blade to remove it from the creping cylinder.

The total application amount of the creping adhesive is preferably in the range of about 0.1 to about 10 lb / ton based on the dry weight of the creping adhesive and the dry weight of the paper web. Unit lb / ton as used herein refers to the dry weight of crepe adhesive measured in lbs relative to the dry weight of the paper measured in tonnes.

The tissue web may include various types of natural fibers, including chemical and mechanical types of wood pulp. Preferred embodiments consist of papermaking fibers of the hardwood and softwood type, wherein at least about 50% of the papermaking fibers are hardwood and at least about 10% are softwood. The tissue web may also include particulate filler.

In a preferred embodiment, the process of the present invention is used to produce tissue paper having a basis weight of about 10 g / m 2 to about 50 g / m 2, more preferably about 10 g / m 2 to about 30 g / m 2. Preferred densities range from about 0.03 g / cm 3 to about 0.6 g / cm 3, more preferably from about 0.05 g / cm 3 to 0.2 g / cm 3.

All percentages, ratios, proportions herein are by weight unless otherwise defined.

The present invention generally relates to creped tissue paper products and methods. More specifically, the present invention relates to dry creped tissue paper, wherein an initial paper web is formed on a fourdrinier or similar paper making device and adhesively fixed to a cylindrical drying drum in a semi-dry state. Here the drying of the web is substantially complete and then creped from the drum by means of flexible creping blades.

1 is a schematic diagram illustrating a papermaking process comprising a preferred embodiment of the present invention comprising a novel adhesive for dry creping a tissue paper.

With regard to the scope of the invention, the invention is specified in the present description and the appended embodiments. This description is provided to aid the understanding of the present invention, not to limit the invention, the scope of the invention being defined by the claims that specifically point out and specifically claim what is considered to be the invention.

As used herein, the term "comprising" means that various components, components, or steps may be used together in the practice of the present invention. Thus, the term "comprising" includes more restrictive terms such as "consisting essentially of" and "consisting of."

As used herein, the term “water soluble” refers to a substance that is dissolved at least 3% by weight in water at 25 ° C.

As used herein, the term "tissue paper web, paper web, web, paper sheet and paper product" all refers to forming an aqueous furnish for papermaking, and depositing the furnish on a small spherical surface, such as a forward linear wire. And removing water from the furnish, for example with or without pressurization by means of specific gravity or vacuum-assisted drainage, and as a final step attaching the semi-dry sheet to the surface of the Yankee dryer Removing the water from the Yankee dryer by means of flexible creping blades, and winding the formed sheet to a reel, all of the paper sheets produced by the evaporation. Refers to.

The terms " multilayer tissue paper web, multilayer paper web, multilayer web, multilayer paper sheet and multilayer paper product " all preferably refer to different fiber types (relatively soft wood and relatively short, typically used for tissue paper production). Refers to a paper sheet made from two or more layers of paper-based aqueous furnish composed of hardwood), all of which are used interchangeably in the art. The layers are preferably formed from the deposition of a separate thin fiber slurry stream on one or more endless spherical surfaces. If each layer is formed on a separate globular surface, the layers can be joined continuously when wet to form a multilayer tissue paper web.

As used herein, the term "single-ply tissue product" means composed of a single layer of creped tissue. The plies may be substantially homogeneous in nature or may be multilayer tissue paper webs. As used herein, the term "multiple tissue product" means that the product consists of one or more creped tissues. The plies of the multiply tissue product may be substantially homogeneous in nature or may be a multilayer tissue paper web.

In the most common form, the present invention is an aqueous dispersion useful as a creping adhesive comprising cationic starch. The dispersion contains about 90 to about 99.9% water, more preferably about 95% to about 99.9% water, wherein the cationic starch is substituted in the range of about 0.001 to about 0.2 cationic substituents per anhydroglucose unit of starch. Has a degree.

As used herein, the term "aqueous dispersion" refers to a composition that consists mainly of water and contains one or more additive ingredients homogeneously distributed throughout the composition. An essential factor is the homogeneity of the composition. Not all components are dissolved at the molecular level. Thus, "aqueous dispersion" includes the more restrictive term "aqueous solution".

As used herein, the term "cationic starch" is defined as starch which is naturally occurring and further chemically modified to impart a cationic constituent moiety. Starch is preferably derived from corn or potatoes, but may also be derived from other raw materials such as rice, wheat or tapicoa. Particular preference is given to starches made from waxy corn, which are also industrially known as amioca starches. Amyostarch is composed only of amylopectin and thus differs from conventional dent corn starch, whereas conventional corn starch contains both amylopectin and amylose. Various unique properties of Amioka starch are described in "Amioca-The Starch from Waxy Corn", H. H. Schopmeyer, Food Industries, December 1945, pp. 106-108.

Cationic starch can be generally classified as follows. (1) tertiary aminoalkyl ethers, (2) onium starch ethers including quaternary amines, phosphonium and sulfonium derivatives, (3) primary and secondary aminoalkyl starches, and (4) other (imino starches, etc. ). Although new cationic products continue to be developed, commercially predominantly tertiary aminoalkyl ethers and quaternary ammonium alkyl ethers are predominant and are preferred for use in the present invention. Suitable starch is produced under the trade name RediBOND ^R by National Starch and Chemical Company, Bridgewater, NJ. Grades with only cationic residues such as Readybond 5320 ^R and Readybond 5327 ^R are suitable, in addition to those with additional anionic functional groups such as Readybond 2005 ^R.

In one embodiment of the present invention, starch preferably comprises about 10% to about 70% of the dry weight of the dispersion, and about 30% to about 90% of the dispersion is occupied by polyvinyl alcohol.

Any polyvinyl alcohol suitable for forming the adhesive film can be used in the present invention. Prior art, such as Bates's US Pat. No. 3,926,716, describes polyvinyl alcohol types that are particularly suitable for application. Commercial sources of polyvinyl alcohol in solid form include Airvol® ^R from Air Products Company, Allentown, Pa. And E. Wilmington, Delaware, USA. children. A variety of trade names are available, including Elvanol ^R from the EI duPont de Nemours. These resins readily dissolve in water to form aqueous solutions, which are easily sprayed and applied to Yankee dryers or semi-dry tissue webs.

The polyvinyl alcohol is preferably partially hydrolyzed polyvinyl acetate having a degree of hydrolysis of at least about 80%, more preferably from about 80% to about 95%.

The molecular weight range of the polyvinyl alcohol useful in the present invention is from about 90,000 to about 140,000. An indirect measure of molecular weight is viscosity, as used herein refers to that of a 4% aqueous dispersion of polyvinylalcohol at 20 ° C. The polyvinylalcal of the present invention has a viscosity of at least about 20 centipoise, more preferably at least about 35 centipoise.

In another embodiment of the invention, the dry weight of the aqueous dispersion comprises from about 50% to about 90% cationic starch and further from about 10% to about 50% water soluble thermosetting cationic polyamide-epihalo. Hydrin resins.

Water soluble thermosetting cationic polyamide-epihalohydrin resins include reaction products of epiamides with polyamides containing secondary or tertiary amine groups.

A particularly preferred polyamide-resin Hebrews gave to be epi Delaware Will Hernandez of particulate material mington Les, Inc. (Hercules Inc.) trade name Kymene (Kymene) ^R crepes and trolls (Crepetrol) ^R and Valley Forge, PA Name of hyuton International, Inc. (Houghton International Inc.) of soft material Unicode (Unisoft) ^R and resort Sol (Rezosol) ^R, as well as commercially available in several trade names. These resins are supplied in concentrated solutions in water and only need to be diluted to be easily sprayed for application on Yankee dryers or semi-dry tissue webs.

The basic chemistry of preparing water soluble thermosetting cationic polyamide-epihalohydrin resins is U. S. Patent No. 2,926, 116 to Kiem, Feb. 23, 1960, and U.S. Patent to Oct. 16, 1962. 3,058,873 and US Pat. No. 3,772,076 to Kiem, Nov. 13, 1973, all of which are incorporated herein by reference.

Preferably, the polyamide-epihalohydrin resin comprises a water soluble polymeric reaction product of epichlorohydrin with a water soluble polyamide having a secondary amine group.

In preparing one of the particularly preferred resins, the dibasic carboxylic acid is first reacted with a polyalkylene polyamine, preferably in an aqueous solution, under conditions suitable for producing a water soluble polyamide having a repeating unit of formula (I):

-NH (C _n H _2n HN) _x -CORCO-

Where

n and x are each 2 or more,

R is a divalent hydrocarbon radical of dibasic carboxylic acid having about 3 to 10 carbon atoms.

The preparation of the resin is then completed by reacting the water soluble polyamide with epihalohydrin, in particular epichlorohydrin to form a water soluble cationic polyamide-epihalohydrin thermosetting resin.

Polyamide secondary amine groups are preferably derived from polyalkylene polyamines such as polyethylene polyamide, polypropylene polyamine or polybutylene polyamine and the like, with diethylenetriamine being preferred.

One of the saturated aliphatic dibasic carboxylic acids containing about 3 to 10 carbon atoms is dicarboxylic acid, examples of which include succinic acid, adipic acid, azelaic acid and the like and mixtures thereof. Dicarboxylic acids containing 4 to 8 carbon atoms are preferred, and adipic acid is most preferred.

The molar ratio of polyalkylene and dibasic carboxylic acid is preferably from about 0.8: 1 to about 1.5: 1.

The molar ratio of epihalohydrin and secondary amine groups in the polyamide is from about 0.5: 1 to about 2: 1.

In another preferred aqueous dispersion according to the invention, the dispersion comprises from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein the solids are from about 10% to about 70% cation Starch, about 20% to about 85% polyvinyl alcohol, and about 5% to about 40% water soluble thermosetting cationic polyamide-epihalohydrin resin.

The present invention also provides a method for creping tissue paper. The method of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein the solids contain cationic starches having from about 0.001 to about 0.2 cationic substituents per anhydroglucose unit of starch. Applying an aqueous dispersion comprising a rotary creping cylinder;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

c) contacting the web with a doctor blade to remove it from the creping cylinder.

Another preferred embodiment of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein from about 50% to about 90% of the solids comprises from about 0.001 to about 0.2 cations per anhydroglucose unit of starch Applying an aqueous dispersion to the rotating crepe treatment cylinder, wherein the aqueous dispersion is cationic starch with a sexual substituent and from about 10% to about 50% of the solid is a water soluble thermosetting cationic polyamide-epihalohydrin resin;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

and c) contacting said web with a doctor blade to remove it from the creping cylinder.

Another preferred embodiment of the present invention

a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein from about 10% to about 70% of the solids is from about 0.001 to about 0.2 cations per anhydroglucose unit of starch Cationic starch with a cyclic substituent, about 5% to about 40% of the solids are water soluble thermosetting cationic polyamide-epihalohydrin resins, and about 20% to about 85% of the solids are about polyvinyl alcohols. Applying the aqueous dispersion to the rotary creping cylinder;

b) compressing a tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And

and c) contacting said web with a doctor blade to remove it from the creping cylinder.

The total application amount of the creping adhesive is preferably in the range of about 0.1 to about 10 lb / ton based on the dry weight of the creping adhesive and the dry weight of the paper web. Unit lb / ton as used herein refers to the dry weight of crepe adhesive measured in lbs relative to the dry weight of the paper measured in tonnes.

Manufacture of Tissue Paper Web

Ingredients of Water-based Paper Furnish

It is expected that various wood pulp will generally include the papermaking fibers used in the present invention. However, other cellulose fibrous pulp such as cotton linter, bagasse, rayon and the like can be used and are also included within the scope of the present invention. Wood pulp that may be used in the present invention includes, but is not limited to, mechanical pulps, such as ground wood, thermomechanized pulp (TMP) and chemically modified thermomechanized pulp (CTMP), as well as sulfite and sulfate pulp (sometimes kraft). Chemical pulp). Pulps derived from both hardwoods and conifers can be used.

Both hardwood pulp and softwood pulp, as well as combinations thereof, can be used as papermaking fibers of the tissue paper of the present invention. As used herein, the term "hardwood pulp" refers to fiber pulp derived from wood material of deciduous trees (genus seed), and "softwood pulp" refers to fiber pulp derived from wood material of softwood (seed plant). do. Blends of hardwood kraft pulp (especially eucalyptus) and northern softwood kraft (NSK) pulp are suitable for making the tissue webs of the present invention. Another preferred embodiment of the present invention most preferably comprises a laminated tissue web wherein hardwood pulp, such as eucalyptus, is used for the outer layer (s) and the softwood kraft pulp of the northern provinces forms an inner layer (s). . Fibers derived from recycled paper, which may contain some or all of the above-mentioned fibers, may also be applied to the present invention.

Granular fillers, including clay, calcium carbonate, titanium dioxide, talc, aluminum silicate, calcium silicate, alumina trihydrate, activated carbon, pearl starch, calcium sulfate, free microspheres, diatomaceous earth and mixtures thereof, are used for aqueous papermaking. You can also include it in your furnish.

Other materials may be added to the aqueous paper furnish or the initial web to impart other properties to the product or to improve the papermaking process, without interfering or adversely affecting the advantages of the present invention, examples of which include It is as demonstrated below.

For retention and web strength purposes it is sometimes useful to include starch, in particular cationic starch, as one of the components of the aqueous papermaking furnish. Starches that are particularly suitable for this purpose are produced under the trade name RediBOND ^R by National Starch and Chemical Company, Bridgewater, NJ.

Usually, since the cationic charge biasing compound is supplied to the papermaking process, it is added to the papermaking process to control the zeta potential of the aqueous papermaking furnish. One suitable material is Cypro 514 ^R , a product of Cytec, Stamford, Connecticut.

In addition, a retention aid is added. Multivalent ions can be effectively added to the aqueous papermaking furnish to improve the retention of fine particles that may remain suspended in the papermaking system of the paper machine. Examples of adding alum, for example, have long been known. More recently, polymers with many charge sites along the chain length have been used effectively for this purpose. Both anionic and cationic flocculants are included within the scope of the present invention. Coagulants such as RETEN 235 ^R , a product of Hercules Incorporated, Wilmington, USA, and Acurac 171 ^R , a product of Cytec, Stamford, Connecticut, USA An example of an anionic flocculant. Coagulants such as RETEN 157 ^R , a product of Hercules Incorporated, Wilmington, USA, and Accurac 91 ^R , a product of Cytec, Stamford, Connecticut, USA Examples of acceptable cationic flocculants.

The use of high surface area and high anion charge particulates is widely disclosed in the art for the purpose of improving formation, drainage, strength and retention. See, for example, US Pat. No. 5,221,435, issued June 22, 1993, to Smith, which is incorporated herein by reference. Typical materials for this purpose are silica colloids or bentonite clays. Adding such materials is within the scope of the present invention.

The advantage of the present invention is most particularly realized in the case of paper grades without permanent wet strength. Wet strength resins, especially the polyamide-epichlorohydrin type described in greater detail in other parts of this application, often provide some creep control even when added to an aqueous paper furnish. However, this benefit is often accompanied by the presence of permanent wet strength (often responsible properties) in the product, and the addition of polyamide-epichlorohydrin to the wet finishing stage of the papermaking process is a direct step in creping operations. It can be achieved by using a polymer and therefore is not effective in promoting crepe benefits.

Creped paper products that have a limited strength need to be temporarily wet strength resin because they need to be disposed of from the toilet to a rot or drainage system. Temporary wet strength resins impart wet strength, characterized in that some or all of their performance is lost when left in the presence of water. For temporary lubrication strength, Co-Bond 1000 ^R supplied by National Starch and Chemical Company, and Parez 750 commercially available from Sec, Stanford, Connecticut. (Parez 750) ^B and binder materials from the group consisting of dialdehyde starch or other resins with aldehyde functionalities such as resins disclosed in US Pat. No. 4,981,557 to Bjorkquist, issued January 1, 1991. The patents may be selected and are incorporated herein by reference.

If improved absorbency is needed, surfactants can be used to treat the creped tissue paper webs of the present invention. The surfactant preferably has an alkyl chain of 8 or more carbon atoms. Examples of anionic surfactants are linear alkyl sulfonates and alkylbenzene sulfonates. Examples of nonionic surfactants include alkylglycoside esters such as Crodesta SL-40 ^R , commercially available from Croda Inc. of New York, NY, March 8, 1977. Alkylglycoside ethers as disclosed in US Pat. No. 4,011,389 to WK Langdon et al., And Pegosperse commercially available from Glyco Chemicals, Greenwich, Connecticut. Alkylglycosides including 200 mL ^R and alkylpolyethoxylated esters such as IGEPAL RC-520 ^R commercially available from Rhone Poulenc Corporation, Cranbury, NJ.

As optional components, especially chemical softeners are contained. Acceptable chemical emollients include the well known dialkyldimethylammonium salts such as ditallowdimethylammonium chloride, ditallowdimethylammonium methyl sulfate, di (hydrogenated) tallow dimethyl ammonium chloride, among which di (hydrogenated) tallowdimethylammonium Methyl sulfate is preferred. This particular material is commercially available from the Witco Chemical Company, Dublin, OH under the trade name Varisoft 137 ^R. Biodegradable mono- and di-ester variants of quaternary ammonium compounds may also be used, which are also within the scope of the present invention.

Any of the chemical additives listed above are merely for illustrative purposes and do not limit the scope of the present invention.

Preparation of Water-Based Paper Furnish

It will be appreciated by those skilled in the art that the qualitative chemical composition of the paper furnish, as well as other factors, among other factors, is important for creped papermaking processes. The following technique is suitable for producing an aqueous paper furnish, but its description should not be considered as limiting the scope of the invention, which is defined by the claims set forth at the end of this specification. do.

Papermaking fibers are first prepared by liberating the individual fibers into an aqueous slurry by any conventional method of pulp that is suitably described in the prior art. Then, if necessary, purification is performed in selected portions of the paper furnish.

In a preferred arrangement, a relatively short slurry of papermaking fibers comprising hardwood pulp is produced while separately producing a slurry of relatively long papermaking fibers. The resulting short fiber slurry is transferred to an outer chamber of a three-layer headbox to form a surface layer of a three-layer tissue, wherein the inner layer of the long fiber is an inner chamber of the headbox into which a slurry of relatively long papermaking fibers is transferred. From. The resulting filled tissue web is particularly suitable for application as a single ply tissue product.

In another preferred arrangement, after forming the aforementioned slurry of long and short fibers, the resulting slurry of short fibers is transferred to one chamber of a headbox having two chambers to form a layer of two layer tissue, Another layer of long fibers is then formed from the second chamber of the headbox into which the slurry of the relatively long papermaking fibers is conveyed. The resulting filled tissue webs are particularly suitable for application to multiply tissue products comprising two plies oriented with each ply such that a layer of relatively short papermaking fibers is placed on the surface of the two ply tissue products.

It will be appreciated by those skilled in the art that the apparent number of chambers of the headbox can be reduced by transferring the same type of aqueous paper furnish to adjacent chambers. For example, the headbox with the three chambers mentioned above can be simply used as a headbox with two chambers by essentially transferring the same aqueous paper furnish to any of two adjacent chambers.

Papermaking process

1 is a schematic diagram of a papermaking process comprising a preferred embodiment of the present invention that includes a novel process for dry creping tissue paper. The preferred embodiment shown is described in detail with reference to FIG. 1.

1 is a side view of a preferred papermaking apparatus 80 for producing paper according to the present invention. Referring to FIG. 1, the papermaking apparatus 80 includes a head box 81 including a top chamber 82, an intermediate chamber 82b, and a base chamber 83 having a layer formed thereon; Sliced loops 84; And above and near a breath roll 86, a detector 90, a vacuum suction box 91, a couch roll 92 and a plurality of turning rolls 94. It consists of a forward linear wire 85 looped at. In operation, the first paper furnish is pumped through the upper chamber 82, the second paper furnish is pumped through the intermediate chamber 82b, and the third paper furnish is pumped through the base chamber 83 It is discharged into slice loops 84 above and below linear wire 85 to form an initial web 88 comprising layers 88a, 88b and 88c. Dewatering occurs through the forward linear wire 85 and is assisted by the detector 90 and the vacuum box 91. Because the forward linear wires return in the direction of the arrow, the shower 95 cleans them before the forward linear wires connect with other passages through the breath roll 86. In the web transfer area 93, the initial web 88 is transferred to the spherical carrier fabric 96 by the action of the vacuum transfer box 97. The carrier fabric 96 passes the web from the transfer zone 93 through a vacuum dehydration box 98 through a blow-through predryer 100 and through two turning rolls 101 to a semi-dry initial tissue. The paper web 106 is formed, which is still supported by the spherical carrier fabric 96. In a subsequent step, the web is transferred to a Yankee dryer 108, and then the carrier fabric 96 passes through and around the additional turning roll 101, shower 103 and vacuum dehydration box 105 to loop. It is cleaned and dehydrated by completing it.

Application of Aqueous Dispersion of Crepe Adhesive

The present invention utilizes the application of a creping adhesive comprising starch and an aqueous dispersion of any polyvinyl alcohol and water soluble thermosetting cationic polyamide-epihalohydrin resin.

Preferably, the solids concentration of the aqueous dispersion is about 0.1 to about 10% at the time of application. Most preferably, the solids concentration is about 0.1 to about 5% at the time of application.

While various application methods of creping adhesives are envisaged and are also within the scope of the present invention, methods of applying an aqueous dispersion through a spray boom facing the surface of a Yankee dryer prior to transfer of the semi-dry tissue paper web. This is preferred.

1, the application location of the dispersion through this preferred embodiment is shown by the spray boom 107.

The use of multiple spray booms, each carrying components comprising the present invention, is specifically within the scope of the present invention.

For example, referring to FIG. 1, the spray boom 108 is optional. If possible, dispersions according to the invention may be applied via the spray boom 107 or 108 or both.

Pressurization of the web to the creping cylinder

In the present invention, the tissue paper web, which remains semi-dry, is pressed against the creping cylinder, which is most commonly called a heated dry surface, the so-called Yankee dryer, which is applied to the creping adhesive applied in the previous step. Assisted by

The web is fixed by pressing on the cylinder surface. Most preferably, the semi-dry web is uniformly attached to the dryer by pressurizing with an opposing cylindrical drum. In addition, a vacuum can be applied to the web by pressing the web against the Yankee surface. In addition, many Yankee dryer drums may be used in the present invention.

Referring to FIG. 1, the semi-dry tissue paper web is secured to the cylindrical surface of the Yankee dryer 109 with the aid of adhesive applied by the spray booms 107 and 108. The boom 107 or 108 or both can apply the dispersion according to the invention. The use of the opposing cylindrical vapor drum 102 promotes the attachment of the web. On steam heated Yankee dryer 109, drying is completed by heated hot air circulated through drying hood 110 by a method not shown. The web is then dry creped from the Yankee dryer 109 by a doctor blade 111 called a creping blade to form a Yankee cotton layer 71, an intermediate layer 73 and a Yankee cotton opposite layer 75. It becomes the paper sheet 70. The paper sheet 70 is then wound between rolls 112 and 113 and around the circumference of the reel 115 with a roll 116 over the core 117 located on the shaft 118. The second doctor blade 114, so-called clean blade, is used to remove excess coating liquid from the dryer surface.

Further, with regard to the process conditions for making the exemplary paper sheet 70, the paper web is preferably dried to have a fiber concentration of about 80%, more preferably about 96% prior to creping.

The present invention relates to felt-pressurized crepe treated tissue paper; High bulk pattern dense creped tissue paper; And high volume uncompressed crepe tissue paper, including but not limited to common crepe tissue paper.

The creped tissue paper web of the present invention has a basis weight of 10 g / m ² to about 100 g / m ² . In a preferred embodiment, the filled tissue paper of the present invention has a basis weight of about 10 g / m ² to about 50 g / m ² , and most preferably about 10 g / m ² to about 30 g / m ² . . Creped tissue paper webs suitable for the present invention have a density of about 0.60 g / cm ³ or less. In a preferred embodiment, the filled tissue paper of the present invention has a density of about 0.03 g / m ³ to about 0.6 g / m ³ , and most preferably about 0.05 g / m ³ to about 0.2 g / m ³ .

The present invention can also be applied to multilayer tissue paper webs. Tissue structures formed from layered paper webs were described in US Pat. No. 3,994,771 to Morgan Jr. et al., Issued November 30, 1976, to Carstens, issued November 17, 1981. European Patent Publication No. 0 613 to U.S. Patent 4,300,981, US Patent 4,166,001 to Duning et al., Issued August 28, 1979, and Edwards, published September 7, 1994. 979, all of which are incorporated herein by reference. The layers preferably consist of different fiber types, wherein the fibers are relatively long softwood fibers and relatively short hardwood fibers, which are typically used in multilayer tissue papermaking. Multilayer tissue paper webs suitable for the present invention comprise an inner layer and at least two overlapping layers comprising at least one outer layer adjacent to the inner layer. Preferably, the multilayered numbered paper comprises an inner layer or an intermediate layer, and three superimposed layers having two outer layers, the inner layer being positioned between the two outer layers. The two outer layers preferably comprise the main filament constituents of the relatively short papermaking fibers having an average length of less than about 0.5 to about 1.5 mm, preferably less than about 1.0 mm. These short papermaking fibers typically comprise hardwood fibers, preferably hardwood kraft fibers, and more preferably hardwood kraft fibers derived from eucalyptus. The inner layer preferably comprises the major filament constituents of the relatively long papermaking fibers having an average length of at least about 2.0 mm. These long papermaking fibers are typically softwood fibers, preferably northern softwood kraft fibers. Preferably, most of the fine fillers of the present invention are contained in at least one of the outer layers of the multilayer tissue paper web of the present invention. More preferably, most of the fine fillers of the present invention are contained in both outer layers.

The creped tissue paper product made from a single or multi-layer creped tissue paper web may be a single ply tissue product or a multi-ply tissue product.

Equipment and methods are well known to those skilled in the art. In a typical process, low density pulp furnish is provided in a pressurized headbox. The headbox has openings for moving thin deposits of pulp furnish on the forward linear wires to form a wet web. The web is then dewatered to typically have a fiber concentration of about 7 to about 25% (based on the total web weight) by vacuum dewatering.

A more preferred variant of the papermaking process of the present invention is the so-called pattern dense method, wherein the structure produced in this method is relatively high, dispersed in a relatively high bulk field and a high bulk field of relatively low fiber concentration. It is characterized by having a series of dense regions of fiber concentration. The high bulk field, on the other hand, features the field of the pillow area. Dense areas are otherwise referred to as knuckle areas. The dense regions may be spaced apart in the field of high bulk or interconnected in whole or in part in the field of high bulk. Preferably, regions of relatively high density are continuous and fields of high bulk are discontinuous. A preferred method of making pattern dense tissue webs is US Pat. No. 3,301,746, Peter Rat, issued January 31, 1967 to Sanford and Sisson. 3,974,025, Paul D., issued to Peter G. Ayers on August 10, 1976. Paul D. Trokhan, issued 4 March 1, 1980, issued by Paul D. Trokhan. No. 4,637,859 issued to Trocan on 20 January 1987, 4,942,077 issued to Wentt on July 17, 1990, and Hyland, published September 28, 1994. European Patent Publication No. 0 617 164, and European Patent Publication No. 0 616 074 to Hermans et al., Published September 21, 1994, all of which are incorporated herein by reference. do.

To form a web of dense pattern, the web is immediately transferred to the forming fabric rather than felt after the web is formed. The web is juxtaposed against a series of supports comprising the molded fabric. By pressing the web against a series of supports, a dense region of the web is formed where it geometrically corresponds to the point of contact between the wet web and the series of supports. The rest of the uncompressed web during this operation is called a high bulk field. This high bulk field can also be reduced in density using hydraulics such as vacuum devices or blow dryers. The web is dewatered and optionally pre-dried in a way that substantially avoids compressing high bulk fields. Preferably, it can be de-densed using hydraulic pressure such as a vacuum device or blow dryer or by mechanically pressing the web against a series of supports. The operation of dehydration, any predrying, and dense zone formation may be integrated or partially integrated to reduce the overall number of process steps performed. The moisture content of the semi-dry web at the point of transfer to the Yankee surface is less than about 40%, allowing hot air to pass through the semi-dry web while the semi-dry web forms a low density structure on the forming fabric.

The web of dense pattern is transferred to a Yankee dryer and completely dried, preferably with no mechanical pressure. In the present invention, preferably, about 8 to about 55% of the surface of the creped tissue paper comprises dense knuckles having a relative density of at least 125% of the density of the high bulk field.

The series of supports is preferably a print carrier fabric having a patterned replacement knuckle that acts as a series of supports that facilitate the formation of dense areas when pressure is applied. The pattern of knuckles constitutes a series of supports as already mentioned. U.S. Patent No. 3,301,746, issued to Jan. 31, 1967 to Sanford and Seathorn by the Print Carrier Fabric; US Patent No. 3,821,068, issued May 21, 1974 to Salvucci Jr. et al .; U.S. Patent No. 3,974,025, filed August 10, 1976; US Patent No. 3,573,164, filed March 30, 1971 to Friedberg et al .; US Patent No. 3,473,576, issued October 21, 1969 to Amnus; U.S. Patent 4,239,065 to Trocan, issued December 16, 1980; And US Pat. No. 4,528,239, issued to July 9, 1985 to Trocan, all of which are incorporated herein by reference.

Most preferably, the web is hydraulically adapted to acclimate the initial web to the surface of the open mesh drying / printing fabric and then thermally pre-dried on the fabric as part of a low density papermaking process.

Another variation of the process steps included within the present invention includes the formation of so-called uncompressed, unpatterned, densely packed multi-layer tissue paper structures, such as Joseph El. Salbuxi Junior and Peter En. US Patent No. 3,812,000, issued to Peter N. Yiannos on May 21, 1974, and Henry E. Y. Becky (Herny E. Becker), Albert L. 4,208,459, issued June 17, 1980 to Albert L. McConnell and Richard Schutte, both of which are incorporated herein by reference. Generally, uncompressed, non-patterned, dense, multi-layer tissue paper structures deposit paper furnish on small spherical forming wires, such as forward linear wires, to form wet webs, dewater webs, and Prepared by removing residual water without mechanical compression until the fiber concentration is at least% and creping the web. The water is removed from the web by vacuum dehydration and thermal drying. The resulting structure is a soft but weak high bulk sheet of relatively uncompressed fiber. It is desirable to apply the bonding material to a portion of the web before creping.

As a practical advantage of the present invention, it is possible to improve the speed of the papermaking operation to improve the attachment or adjustment of the sheet between the creping blade and the reel.

Without being limited by theory, the reason why the present invention provides excellent adhesion will be described below. Cationic starch is a special adhesive for cellulose pulp that has cellulose-like carbohydrate structure and surface charge properties, which can provide very high adhesive strength. In addition, this starch is rewetable and can be improved using polyvinyl alcohol or a water soluble cationic polyamide-epihalohydrin resin to improve the removability while maintaining the high adhesion properties of the cationic starch.

As used herein, “strength” means total tensile strength, the method of determining that measurement is disclosed in the following paragraphs. The tissue paper web according to the invention is strong. This generally means that the total tensile strength is at least about 100 g / in, more preferably at least about 300 g / in.

The tissue paper webs of the present invention can be used where soft absorbent tissue paper webs are desired. In particular, the use of the tissue paper web of the present invention is particularly advantageous for toilet tissues and cosmetic tissue products. Single and multi-ply tissue paper products can be made from the web of the present invention.

Analysis and test procedure

A. Density

As used herein, the density of a multi-layer tissue paper is the average density calculated by dividing the basis weight of the paper by the caliper, according to the appropriate unit conversion embedded therein. The caliper of the multi-layer tissue paper as used is the thickness of the paper when subjected to a compressive load of 95 g / in ² (15.5 g / cm ² ).

B. Molecular Weight Determination

The distinguishing feature of a polymeric material is the size of its molecular weight. Almost all of the properties that polymers can be used for a variety of applications are extracted from their huge molecular properties. In order to fully characterize these materials, it is important to have a means for partitioning and determining their molecular weight and their distribution. It is more accurate to use the term molecular weight rather than relative molecular mass, but the latter is more commonly used in the polymer art. Determining the molecular weight distribution is not always practical. However, this has become more common using chromatographic techniques. Rather, the molecular size is expressed based on the molecular weight average.

Molecular weight average

Given a simple molecular weight distribution representing the weight piece Wi of a molecule having a relative molecular mass Mi, it is possible to define several useful average values. The average running on the basis of the number of molecules (Ni) of a specific size (Mi) gives the number average molecular weight.

An important consequence of this definition is that the number average molecular weight includes avogadro number of molecules per gram. This definition of molecular weight is consistent with that of the monodisperse molecular species, i.e. molecules of the same molecular weight. It is more recognizable that Mn can be easily calculated if the number of molecules in a given mass of a polydisperse polymer is somehow determined. This is the basis for comprehensive property measurement.

The mean for the basis of the weight piece Wi of the molecule of a given mass Mi yields the definition of the weight average molecular weight.

Where

Mw is used in the present invention because it is more useful for expressing polymer molecular weight than Mn because it more accurately reflects such properties such as the melt viscosity and mechanical properties of the polymer.

C. Panel Ductility Measurement of Tissue Paper

Ideally, before making ductility measurements, the paper sample to be tested should be conditioned according to Topp Method # 402OM-88. Here, samples are preconditioned for 24 hours at a relative humidity level of 10 to 35% at 22-40 ° C. After this preconditioning step, the sample should be adjusted for 24 hours at a relative humidity level of 48-52% at 22-24 ° C.

Ideally, the ductility panel test is conducted in a thermo-hygrostat area. If this is not possible, all samples, including the regulator, should be done under the same exposure environmental conditions.

Ductility tests are incorporated herein by reference and are published in the American Society for Testing and Materials, 1968, "Special Manual for Sensory Testing Methods," ASTM Special Technical Publication No. 434. As compared to a pair in a form similar to that described in the " Ductility is assessed by subjective testing using what is referred to as the paired difference test. This method uses the reference appearance for the test material itself. For softness perceived by tactile sense, two samples are provided so that the subject cannot see the sample, and the subject is required to select one of them based on the tactile recognition method. The results of the test are reported in a form called Panel Score Unit (PSU). In connection with the ductility test to obtain ductility data reported here in the form of PSUs, a number of ductility panel tests are performed. In each test, ten ductility judgments made are required to evaluate the relative ductility of three sets of paired samples. Sample pairs are evaluated one pair at a time in each judgment: one sample of each pair is designated X and the rest are designated Y. In short, each X sample is rated for its partner Y sample as follows:

1. If X is judged to be slightly softer than Y, it is given a rating of +1; if it is determined that Y may be slightly softer than X, it is given a rating of -1;

2. If X is clearly slightly softer than Y, then a rating of +2 is given; if Y is clearly slightly softer than X, then a rating of -2 is given;

3. If X is judged to be considerably softer than Y, then a rating of +3 is given, and if Y is obviously considerably softer than X, then a rating of -3 is given;

4. If X is judged to be slightly softer than Y, then a rating of +4 is given, and if Y is considerably softer than X, a rating of -4 is given.

Grades are averaged and the resulting values are expressed in units of PSU. The resulting data is considered as the result of one panel test. Once more than one sample pair is evaluated, all sample pairs are ordered according to their rank by statistical analysis using the pair. The rating is then adjusted up or down depending on the value, i.e., the value that is required to give a zero PSU value so that the sample is selected to be a zero base reference for the zero PSU value. The other samples then have a + value or a-value that is determined by their rank relative to the zero base criterion. The number of panel tests performed and averaged means a significant difference in ductility at which about 0.2 PSU is subjectively perceived.

D. Measuring the Strength of Tissue Paper

Tensile Strength at Dry State

Tensile strength was measured in a 1-in. Wide strip using the Swing-Albert Intelect II standard tensile strength test (Swing-Albert Instrument Corporation, 10960 Philton, Dutton Road, Philadelphia, 19534, Pennsylvania). Is determined. This method is intended to be used for paper finished products, reel samples, and raw materials.

Sample adjustment and manufacture

Before the tensile strength test, the paper sample to be tested should be adjusted according to Top Skin Method # T402OM-88. All plastic and paper board package materials should be carefully removed from the paper samples before testing. Paper samples should be adjusted for at least 2 hours at a relative humidity level of 48-52% at 22-24 ° C. All aspects of sample preparation and tensile strength testing should be limited to the constant temperature and humidity room.

In finished products, the damaged product is discarded. Thereafter, five strips are removed from the four available units (also called sheets), and one is stacked on top of the other to form a long stack as a through hole between the matched sheets. Sheets 1 and 3 are identified for mechanical tensile strength measurements and sheets 2 and 4 are identified for transverse tensile strength measurements. Next, the JDC-1-10 or JDC with safety cutouts from the Swing-Albert Instrument Corporation, Durton Road 10960, Philadelphia, 19534, Pennsylvania, to create four separate materials. -1-12) to cut through hole line. Stack 1 and Stack 3 are still identified for the mechanical tensile strength test, and Stack 2 and Stack 4 are identified for the transverse test.

Two 1 inch wide strips are cut from the stack 1 and stack 3 in the machine direction. Two 1 inch wide strips are cut transversely from stacks 2 and 4. There are now four 1 inch wide strips for machine tensile test and four 1 inch wide strips for transverse tensile test. For finished product samples, eight 1 inch wide strips are available 5 unit (also referred to as sheet) thicknesses.

For raw materials and / or reel samples, a 15-inch by 15-inch paper cutter (Swing-Albert Corporation, Dutton Road 10960, 19534, Philadelphia, Pennsylvania) with an 8-ply thickness from the portion of interest of the sample. Cut using JDC-1-10 or JDC-1-12) equipped with a safety shutoff device from Instrument Corporation. Note that one 15 inch cut should be performed in a direction parallel to the machine direction and the other 15 inch cut should be performed in a direction parallel to the transverse direction. Paper samples should be adjusted for at least 2 hours at a relative humidity level of 48-52% at 22-24 ° C. All aspects of sample preparation and tensile strength testing should be limited to a constant temperature and humidity room.

From this pre-adjusted 15 inch by 15 inch standard sample, four 1 inch by 7 inch strips are cut, with the long 7 inch side parallel to the machine direction. These samples are stored as machine direction reels or raw product samples. Cut another four 1 inch by 7 inch strips, with the long 7 inch side parallel to the transverse direction. These samples are stored as transverse reels or as raw sample material. All cuts have already been cut using a paper cutter (JDC-1-10 or JDC-1-12 with a safety cutout from Swing-Albert Instrument Corporation, Durton Road 10960, 19534, Pennsylvania). Note that it was cut. Now there are a total of eight samples: four of them are 8-ply 1in × 7in strips, 7in side parallel to the machine direction, and four are 8-ply 1in × 7in strips, 7in side becomes parallel to a horizontal direction.

Tensile Strength Test Work

For a practical measurement of tensile strength, a Swing Albert Intelligent II Tensile Strength Tester (Swing-Albert Instrument Corporation, Durton Road 10960, Philadelphia, 19534, Pennsylvania) is used. Insert a flat face clamp into the device and calibrate the tester according to the instructions given in the Operating Instructions of the Swing Albert Intelligent II. Set the instrument crosshead speed to 4.00 inches / minute and the first and second gauge lengths to 2 inches. Rupture sensitivity should be set to 20g, sample width set to 1in, and sample thickness set to 0.025in.

The load cell is chosen such that the expected tensile strength for the sample results to be tested is between 25% and 75% of use. For example, a 5000g load cell may be used for a sample having an expected tensile strength range of 1250g (25% of 5000g) to 3750g (75% of 5000g). Tensile strength testers can be set in the 10% range of a 5000g load cell so that samples with an expected tensile strength of 125g to 375g can be tested.

Take one of the tension strips and place one end thereof in one clamp of the tensile strength tester. The other end of the paper strip is placed in the other clamp. Note that the long side of the strip is to be parallel to the side of the tensile strength tester. Also note that the strips do not hang on either side of the two clamps. In addition, each pressure of the clamp must be in complete contact with the paper sample.

After inserting the paper test strips into the two clamps, the tensile strength of the equipment can be observed. If the tensile strength of the device shows more than 5g, the sample is too taut. Alternatively, if a period of 2-3 seconds has elapsed since the start of the test but before any value is recorded, the tension strip is stretched too much.

Run the tensile strength tester as described in the Tensile Strength Tester Equipment Guide. The test is complete after the crosshead automatically returns to its initial starting position. Read and record the tensile strength load in g from the instrument scale or digital panel meter in the vicinity of the instrument.

If the reset state is not performed automatically by the instrument, make the necessary adjustments to set the instrument clamp to its initial starting position. As mentioned above, the following paper strip is inserted into two clamps to obtain tensile strength measurements in g. Tensile strength measurements are obtained from all paper test strips. It should be noted that during the test the reading should not be read if the strip slips or ruptures at the edge of the clamp.

Calculation

For four machine direction 1 inch wide finished strips, four separate recorded tensile strength measurements are added together. This sum is divided by the number of strips tested. This number should normally be four. In addition, the sum of the tensile strength values reported is divided by the number of units available per tensile strip. This is generally 5 for both single and double ply products.

Repeat the calculation for the transverse finished strip.

For raw machined or reel samples in the machine direction, four separately recorded tensile strength measurements are combined. Divide this sum by the number of strips tested. This number should normally be four. In addition, the sum of the tensile strength values reported is divided by the number of units available per tensile strip. This is generally eight.

This calculation is repeated for untranslated or reel sample paper strips.

All results are in g / in.

The following examples are presented to illustrate the practical use of the present invention. This example is for the purpose of illustrating the invention and should not be construed as limiting the scope of the invention. It is intended that the invention only be limited by the appended claims.

First, about 3% concentration aqueous slurry of Northern Softwood Crafts (NSK) was made using a conventional pulp mill, and then the raw material pipe was passed through the headbox of the forewood linear.

To impart temporary wet strength to the finished product, a Co-BOND 1000 ^R 1% dispersion was prepared and added to the NSK raw pipe at a rate sufficient to mix 1% Co-BOND 1000 ^R based on the dry weight of the NSK fibers. It was. The treated slurry was passed through an in-line mixer to improve absorption of the temporary wet strength resin.

The NSK slurry was diluted to about 0.2% concentration using white water in a fan pump.

About 3% by weight aqueous slurry of eucalyptus fibers was prepared using a conventional repulp maker.

Eucalyptus was passed through a feed pipe to another fan pump, and the eucalyptus was diluted to about 0.2% concentration using white water in the fan pump.

The NSK and eucalyptus slurries were transferred into headed boxes with multichannels with appropriately loaded layers of leaves and held in separate streams until discharged on the moving forward linear wires. A headbox with three chambers was used. Eucalyptus slurry containing 80% by weight of the final paper (dry) is transferred to the chamber to form two outer layers, and NSK slurry containing 20% by weight of final paper (dry) is transferred to the chamber and between the two eucalyptus layers A layer was formed. When discharging the contents of the headbox, the NSK and eucalyptus slurries were mixed to form a composite slurry.

The composite slurry was drained onto the moving forward linear wire and then dehydrated with the aid of a detector and a vacuum box.

An initial wet web with a fiber concentration of about 15% at the time of transfer was a 5-shed satin, with 84 machine direction monofilaments and 76 machine vertical monofilaments and about 36% knuckle areas, respectively, per inch from the forward linear wire. The patterned molding fabric was transferred to a 5-shed satin weave structure.

Further dehydration was performed by vacuum draining until the web had a fiber concentration of about 28%.

In contact with the patterned molding fabric, it was predryed by aeration blow until the patterned web had a fiber concentration of about 62% by weight.

The semi-dry web was then attached to the surface of a Yankee dryer having a 10 ft diameter with the aid of a sprayed creping adhesive comprising a 0.25% aqueous solution of the composition selected from Table 1 below. Selected compositions represent Examples 1-8. Examples 1, 2 and 3 correspond to polyvinyl alcohol and mixtures of polyvinyl alcohol and polyamide-epichlorohydrin resins as described in the prior art. Examples 4, 5, 6, 7 and 8 are compositions according to the invention.

The experiment was designed as an experiment using a mixture of three variables, and the compositions for Yankee dryer application were chosen in random order.

Example number Polyvinyl alcohol Cationic starch Polyamide-Epichlorohydrin (PAE) Resins One 100% 0% 0% 2 70% 0% 30% 3 85% 0% 15% 4 0% 70% 30% 5 0% 100% 0% 6 0% 85% 15% 7 50% 50% 0% 8 35% 35% 30%

Polyvinyl alcohol was an Airvol 540 ^R purchased from Air Products Company, Allentown, PA.

Cationic starch was RediBOND 5320 ^R purchased from National Starch and Chemical Company, Brigewater, NJ.

The polyamine-epichlorohydrin resin was Kymene 557H ^R purchased from Hercules Inc., Wilmington, Delaware.

The selected creping adhesive was sprayed onto the Yankee surface through a spray boom equipped with three nozzles spaced across the width of the dryer. The nozzle was model number 650050, purchased from Spraying Systems Inc., Wheaton, Illinois. The nozzle was positioned about 25 cm away from the surface, facing the dryer surface. The boom was positioned about 1 m from the point where the semi-dry web contacted the Yankees. The boom was pressurized to about 100 psi. This pressurized level spray nozzle sprayed the creping adhesive at a rate of about 1.7 lb / ton creping adhesive solids based on the dry weight of the web.

The fiber concentration was increased to about 96% prior to creping the web from the Yankee using a doctor blade.

The doctor blade had a tilt angle of about 25 ° and was positioned to provide an impact angle of about 81 ° for the Yankee dryer.

The percentage of crepes was adjusted to about 18% by running the Yankee dryer at about 800 feet per minute (about 244 m per minute) and the drying web was rolled at a rate of 656 fpm (201 meters per minute).

The degree of adhesion of the web to the dryer was measured by measuring the tensile strength of the sheet using a web tensiometer located on the web moving between the creping blade and the reel.

The finished web was applied as a three layer single ply creped patterned, dense tissue paper product having a basis weight of about 18 lb per 3000 ft ² .

Web tensile strength measurements for each adhesive formulation were modeled using multivariate regression curves. Three input variables were used to include all possible first and second order boundaries in the regression curve, but the boundaries with less than 95% significance were removed sequentially so that all remaining boundaries were statistically significant in the 95% confidence interval. Had The result is a web tensile strength model such as [web tensile strength =% PVOH × 0.26 +% cationic starch × 0.31 +% PAE × 0.81-% PAE ×% PVOH × 0.70-% PAE ×% cationic starch × 0.56]. Where% PVOH,% cationic starch and% PAE represent the percentage values of each of the polyvinylalcohol, cationic starch and polyamine-epichlorohydrin resin, making up the solids of the aqueous dispersion applied as the creping adhesive ).

The web tensile strength values shown in Table 2, measured using this model, correspond to the adhesive formulations of each example.

Example number Polyvinyl alcohol Cationic starch Polyamide-Epichlorohydrin (PAE) Resins Web tensile strength (g / in) One 100% 0% 0% 25.8 2 70% 0% 30% 27.7 3 85% 0% 15% 25.2 4 0% 70% 30% 34.5 5 0% 100% 0% 31.0 6 0% 85% 15% 31.5 7 50% 50% 0% 28.4 8 35% 35% 30% 31.1

From the above results, it can be seen that the dispersions according to the present invention (Examples 4, 5, 6, 7 and 8) provide higher web adhesion than the prior art dispersions of Examples 1, 2 and 3. Example 8 shows a particularly good balance of adhesion and removal.

Claims (10)

An aqueous dispersion useful as a creping adhesive comprising cationic starch having about 0.001 to about 0.2 cationic substituents per unit of anhydroglucose of starch and containing about 90% to about 99.9% water. The method of claim 1, The cationic starch comprises about 10% to about 70% of the dry weight of the dispersion and further comprises from about 30% to about 90% polyvinyl alcohol of the dry weight of the dispersion. The method of claim 1, Cationic starch comprises from about 50% to about 90% of the dry weight of the dispersion and from about 10% to about 50% of the dry weight of the dispersion, further comprising an aqueous thermosetting cationic polyamide-epihalohydrin resin. Dispersion. The method of claim 3, wherein Cationic starch accounts for about 10% to about 70% of the dry weight of the dispersion, and water soluble thermosetting cationic polyamide-epihalohydrin resin accounts for about 5% to about 40% of the dry weight of the dispersion, dispersion dry weight An aqueous dispersion further comprising from about 20% to about 85% polyvinyl alcohol. The method according to any one of claims 1 to 4, Wherein the polyvinyl alcohol has a degree of hydrolysis of from about 80% to about 95%, and the cationic substituent of the cationic starch is selected from the group consisting of tertiary aminoalkyl ethers, quaternary ammoniumalkyl ethers, and mixtures thereof. The method according to claim 3 or 4, An aqueous dispersion wherein the water soluble thermosetting polyamide-epihalohydrin cationic resin is a reaction product of epihalohydrin and a polyamide precursor having a repeating unit of formula (I): Formula 1 -NH (C _n H _2n HN) _x -CORCO- Where n and x are each 2 or more, R is a saturated aliphatic chain of 3 to 10 carbon atoms. a) from about 90% to about 99.9% water and from about 10% to about 0.1% solids, wherein the solids comprise cationic starches having from about 0.001 to about 0.2 cationic substituents per anhydroglucose unit of starch Applying said aqueous dispersion to a rotary creping cylinder; b) compressing the tissue paper web against the creping cylinder to adhere the web to the surface of the cylinder; And c) contacting the web with a doctor blade to remove from the creping cylinder. The method of claim 7, wherein Creping the tissue paper, wherein the solids comprise from about 50% to about 90% cationic starch and further comprise a water-soluble thermosetting cationic polyamide-epihalohydrin resin in an amount from about 10% to about 50%. Way. The method of claim 7, wherein The solids comprise from about 10% to about 70% of cationic starch and further from about 5% to about 40% of the water-soluble thermosetting cationic polyamide-epihalohydrin resin and from about 20% to about 85% Crepe processing method of the tissue paper containing polyvinyl alcohol. The method of claim 9, Wherein the water-soluble thermosetting cationic polyamide-epihalohydrin resin comprises a reaction product of epihalohydrin and a polyamide precursor having a repeating unit of formula (I): Formula 1 -NH (C _n H _2n HN) _x -CORCO- Where n and x are each 2 or more, R is a saturated aliphatic chain of 3 to 10 carbon atoms.